An instrument...this could be something used by a doctor to perform surgery, a tool used by a mechanic, or anything that a skilled person uses to perform a specific task. Even in music, an instrument is used by a skilled person to perform--or to make beautiful music.
When I read Romans 6:13, "Neither yield ye your members as instruments of unrighteousness unto sin: but yield yourselves unto God, as those that are alive from the dead, and your members as instruments of righteousness unto God," I imagine the Lord as being a skilled Musician. Then I apply this verse to my heart. Am I an instrument in His hands? I want to be an instrument in His hands used to make beautiful music. Do you?
Of course, instruments require some tuning every once in a while. Thankfully His ears listen to me every day and can tell when something is not "sounding right." In order for Him to make something beautiful out of my life, He needs to tune me first. I need to yield to His every "twisting and turning" of the strings, and let Him "pluck the strings" until they sound just right. After I have yielded myself completely to Him in the tuning process, He will begin to make music out of my life.
Tuning takes time----so if you find yourself in the process of being "plucked," just be patient. Sooner or later the Skilled Musician will begin to make a sweet sound from you, others will be blessed, and the Master Musician will be glorified in the masterpiece He has created!
The key is to just yield..and whisper, "Just Play Me."